Another Rad/cap/boiling issue...

Hi all - I've already read a lot of threads on here but mine is a little more specific and would like to get the benefit of the collective opinion.
I have a 2010 Rocket Tourer and it has had occasional issues with the cooling system i.e. the cap went and it had a stone hole in the RAD. It also had the front end rebuilt after some insurance work (why they had to touch any of that, god only knows, as the only damage was cosmetic when someone kindly knocked the bike over when it was on its side stand).
Anyway, that aside...
If I go on a ride and the weather is even vaguely warm, everything is normal when in use and everything does as it should.
However, when I stop occasionally the coolant from the header tank deposits itself under the bike.
I've changed the radiator cap (twice - current is a 1.4Bar versus the 1.2 genuine Cap (I did that when the vacuum/return valve started weeping out of the cap itself).
Rad was fully reconditioned (red herring maybe - the symptoms were there before and after this).

So I suspect the water in the heads is boiling when I stop the bike (often the fan is running at that point which goes off when I turn off the ignition) which creates excess pressure which blows out the water in the header.

I've just bought a flushing fluid and new antifreeze in case the repairer filled it with an antifreeze that reacted with the anti-freeze that was already in there and of course I've also bought more anti-freeze to fill it when flushed. Not done it yet, its en route from the supplier.
Given I think this is a boiling issue is there anything else I can do to reduce the risk of this as currently I carry fluid to top up the header but that by its very nature is going to impact the anti-freeze/water ratio and to be blunt I'd rather it didn't blow out in the first place. Change the RAD cap to a 1.8 or is that now in to risky territory with the hoses and Radiator pressures etc>

Are you overfilling the rad? You should only top up to the lower line on the expansion tank when the bike is cold. Coolant will expand to the max line when up to temp. Any more coolant than that will puke out the overflow tube,

Sounds like the radiator is not getting sufficient air flow, or your water pump is blocked The fan kicks on over 200 degrees from a thermostatic switch. The fan continues to run until the temperature in the coolant drops the switch out. Going higher pressure will raise the boiling point but you are aware of the potential risks of doing that. I would start at the basic, the water pump. If the pump is air/vapor bound you can get the results you're experienceing. If the pump checks out next is the radiator finning is clearof debris. The heat exchange effectiveness is directly related to the air flow across the fins (assuming the coolant flow is optimized).

atomsplitter said:

Sounds like the radiator is not getting sufficient air flow, or your water pump is blocked The fan kicks on over 200 degrees from a thermostatic switch. The fan continues to run until the temperature in the coolant drops the switch out. Going higher pressure will raise the boiling point but you are aware of the potential risks of doing that. I would start at the basic, the water pump. If the pump is air/vapor bound you can get the results you're experienceing. If the pump checks out next is the radiator finning is clearof debris. The heat exchange effectiveness is directly related to the air flow across the fins (assuming the coolant flow is optimized).

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Thanks - the radiator was effectively reconditioned recently and all looks clean. The fan stops as soon as I turn off the ignition though?.

jake shaw said:

Are you overfilling the rad? You should only top up to the lower line on the expansion tank when the bike is cold. Coolant will expand to the max line when up to temp. Any more coolant than that will puke out the overflow tube,

Click to expand...

Aha, I usually fill it to the top. Its only ever dropped to 'low' so maybe I'm trying to fix a problem that isn't actually there and its user error? Some other suggestions are coming in so maybe I'll hang fire on the flush, drop the level (or just not fill it up again) and wait to see if it happens again.

jake shaw said:

Are you overfilling the rad? You should only top up to the lower line on the expansion tank when the bike is cold. Coolant will expand to the max line when up to temp. Any more coolant than that will puke out the overflow tube,

Click to expand...

plus 1
make sure that all the air is out of system by loosing the air bleed screw by the thermostat.
let it puke out what it don't need then leave it like that.

Another factor to consider is your coolant mixture.
More is better does not apply to antifreeze in cooling systems, when it comes to thermal efficiency.
Ethylene glycol is used to prevent freezing in frigid climates and also has anti corrosive properties, which is advantageous.
Water has a better thermal efficiency than ethylene glycol. i.e. it can transfer heat from the block to the radiator better.
People often run with the 50/50 mix, as they think more is better, when in actuality 30/70 ethylene glycol/water has better cooling capacity and still provides antifreeze and corrosion prevention.
Mixing different brands of coolant can cause a chemical reaction and create goop that will rapidly block the fine tubes of the radiator, at best and eat out the alloys of the system, at worst. I've seen it happen, often.
So, if ever topping up system use only water. Demineralised is best.
13 years experience in cooling system industry.

Bosco15 said:

So, if ever topping up system use only water. Demineralised is best.
13 years experience in cooling system industry.

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One note (no argument to above) do not make the mistake of confusing "distilled" with "demineralized." Distilled water is just that, it has been boiled and cooled, removing the suspended solids in the process, but many chemicals are volitile and are carried over with the distilling process. Any volitiles in the water (like sulphates) can plate out on components in the water stream setting up conditions for corrosion. Demineralizaation on the other hand is done using anion and cation beds removing everything in the water stream that isn't H2O. The result (if done properly) has a very very low conductivity (i.e. will not conduct electrically) and has nothing in it that can plate out on components.

To illustrate this point, large steam turbine generators use demineralized water for cooling inside the stator bars in the generator. The GE unit at Wolf Creek Generating station produces 25,000 volts at 31,000 amps output at full power. Anything in the water in the stator water that could conduct electricity would arc across the stator bar potentailly holing the copper stator bars from mini lightning bolts. Distilled water would cause arcing and sparking in the stator so is not used.

Rocketdave said:

Aha, I usually fill it to the top. Its only ever dropped to 'low' so maybe I'm trying to fix a problem that isn't actually there and its user error? Some other suggestions are coming in so maybe I'll hang fire on the flush, drop the level (or just not fill it up again) and wait to see if it happens again.

Click to expand...

Problem solved... don't overfill the overflow tank.

If you are concerned about the water temperature getting too high, I'm pretty sure you can connect TuneECU to see what it climbs to. You can watch to see what temp the fan turns on at and if the temp holds steady or drops with the fan running. If the fan is turning on and off, your bike isn't overheating. I purposely reduced the temp my fan turns on from 100C to 98C because I don't like temps climbing to the boiling point of water even though the cooling system can handle it... personal fetish. Your fan will turn off as soon as the ignition is shut off. This is one quirk I wish Triumph would address. A lot of vehicles will run the fan after shutting off the engine to prevent boiling. Triumph doesn't, at least on the Rocket.

Bosco15 said:

People often run with the 50/50 mix, as they think more is better, when in actuality 30/70 ethylene glycol/water has better cooling capacity and still provides antifreeze and corrosion prevention.

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While this is true, I would not recommend it if you park your Rocket in an unheated area where temps get very cold (like where I live)... 30/70 protects you down to 8.6F and 50/50 down to -35F. Since I live in an area that often gets down to -40F in winter, I have my antifreeze water mix slightly higher than 50/50 checked with a hydrometer. In this instance, more is better. If you live in the south, who cares.... ride